Magnetophoresis is the motion of dispersed magnetic particles relative to a fluid under the influence of a magnetic field. The movement of magnetic particles can be used to detect or isolate specific components in the fluid, using specific binding and or capture. Such magnetic particles can be manipulated by applying an external field, which exerts a force in proportion to the gradient of the field. In most work to date, field gradients have been applied using macroscale (millimeter scale and larger, where 1 millimeter, mm, =10−3 meters) electromagnet systems, or microscale (micrometer scale, where 1 micrometer, μm, also called a micron=10−6 meters) lithographically-defined field-generating circuits. These approaches are inherently long-range and are difficult to scale down to single-particle control. Moreover, the large fields and field-gradients require several amps of current in field-generating circuits, posing a major challenge in device design, power dissipation, and heating.
Conventional systems for manipulating magnetic particles using magnetic field gradients have involved bench-top approaches requiring large, sophisticated machines. In addition to the power and heating issues associated with such conventional systems as described above, the cost of such systems has been high, and their speed has been low.